Information transmitted as video signals via video transmission equipment arrive at a receiving antenna by a variety of routes, some of which have significantly different path lengths than others. The varying path lengths of the incoming video information can result in a distorted video signal which, in the case of television reception, produces "ghosts". Typical interference and distortion results from reflections from airplanes, known as airplane flutter which tends to alter the path length of the incoming video signal. Examples of fixed causes of interference are buildings and structures in the vicinity of the receiving antenna. While such distortion in the incoming video signal is merely a nuisance which can be tolerated by a home television viewer, the occurrence of a few seconds of interference resulting from the presence of aircraft, can have significant adverse effect on transmitted video information which has a total duration of only a few seconds. An example of such a video transmission is described in detail in U.S. Pat. No. 3,789,137, Time Compression Of Audio Signals, issued Jan. 29, 1974 and assigned to the assignee of the present invention. The system disclosed in the above identified patent compresses many minutes of audio information into a few seconds of pseudo-video information for transmission by a conventional video apparatus for recording on video recording means and subsequent time expansion and conversion into conventional analog audio signals. In such a system, wherein typically a thirty minute audio program is transmitted as a few seconds of pseudo-video information, the occurrence of distortion or other interference for only those few seconds can have a significant adverse effect on the entire 30 minute program. While there are well-known techniques using tapped delay lines to compensate for fixed multi-path distortion, and while it is apparent that the use of elaborate sensing circuits coupled with automatic adjustment of tapped delays and gains can compensate for varying multi-path conditions, such techniques are both expensive and complex.
A technique is described herein which provides a relatively simple and inexpensive method reducing the distortion effects arising from the recurring synchronizing, blanking and code signals in multi-path conditions.